1. Field of the Invention
The invention relates to a method of treating boundary surfaces of a vehicle body, in particular for protection against corrosion, according to the pre-characterizing clause of claim 1 and/or 2, as well as a structural element (corrosion-protection element) suitable for carrying out this method.
2. Discussion of the State of the Art
Protection of a vehicle body against corrosion has for centuries been the goal of intensive development work in vehicle construction, in particular automobile manufacture, and has been steadily improved. The current status is so convincing that most of the large automobile manufacturers can issue many-year guarantees against serious damage to the body by rust.
An essential stage in the process of vehicle-body corrosion protection—in addition to galvanizing important or all parts and a high-quality final lacquering—is immersion in a bath of an anti-corrosion solution, the process of cathodal electrolytic dip-priming (customarily abbreviated CDP). In this process practically all the sheet-metal surfaces are wetted by a highly effective layer of material that protects against corrosion, which adheres firmly to the body when the body is removed from the bath.
Like the rest of modem automobile manufacture, the corrosion-protection stage has now become a highly automated process, in which for reasons of economy there is hardly any opportunity for manual measures to be implemented. Nevertheless, certain regions of vehicle bodies are still at extraordinarily great risk of corrosion, because they include welded points or seams and/or are especially exposed to attack by corrosive media encountered while the vehicle is in use; therefore these regions must be treated manually to protect them from corrosion, even in the present state of technology.
Among these regions is the supporting structure for the MacPherson strut unit, hereinafter referred to as the MacPherson-strut dome. There is customarily an annular gap between a so-called outer dome and inner dome, which are welded together at multiple points to form the strut support. This region, embedded in the lacquering process, is manually provided with an additional cover, by spraying a mass of PVC onto it or brushing on a thick anti-corrosion layer.
This procedure is comparatively inefficient (in the overall context of highly automated manufacture) and involves extra costs. Furthermore, during construction of the vehicle body provisions must be made for it; that is, the region that is to be protected by this means must remain adequately accessible for manual treatment during the lacquering process, i.e. even after substantial vehicle components have been installed in the body.
At other places in a vehicle body, for instance in the region between roof bow and roof of the vehicle, or at metal edges or flanges of the doors and the covers for engine and luggage compartments, there are regions for which an extra corrosion protection is reasonable but, according to the state of the art, can be accomplished only by manual application of an anti-corrosion medium. Like the corresponding measures in the region of the strut-support dome, such corrosion-protection operations are associated with increased personnel effort and hence expense. Furthermore, the relevant regions are in part visible to the eventual user of the vehicle, and the manually executed corrosion-protection measures do not give a convincing visual impression. In the last-mentioned region of a vehicle body, in addition to the corrosion protection it is also necessary for a lining layer to be provided between the outer surfaces and their supports (e.g., roof and roof bow), and this at present is ordinarily produced by manual application of a pasty mass. This process is encumbered by the same disadvantages as are manual corrosion-protection measures.